Study of Nitazoxanide in the Treatment of Clostridium Difficile-associated Disease

Inclusion Criteria: * Age ≥ 18 years. * Patients with new onset of disease evidenced by diarrhea (≥ 3 unformed stools within 24 hours), and one or more of the following symptoms of CDAD: * abdominal pain or cramps * peripheral leukocytosis * fever * C. difficile toxin A or B detected in a stool specimen obtained within 3 days before enrollment by enzyme immunoassay. * Patients willing to avoid the following medications during the study: * oral and intravenous metronidazole * oral vancomycin * anti-peristaltic drugs * opiates (patients on opiates may be included in the study if they were taking opiates prior to enrollment and the dose is not increased during the study) * Saccharomyces cerevisiae (baker's yeast) * Lactobacillus GG * cholestyramine * colestipol Exclusion Criteria: * Patients with other known causes of diarrhea or colitis (e.g., Shigella, Salmonella, Cryptosporidium parvum, Giardia lamblia, Entamoeba histolytica, inflammatory bowel disease, irritable bowel syndrome, advanced AIDS or chemotherapy for malignancy). * Patients that commonly have 3 or more stools per day and/or severe abdominal pain in the absence of CDAD. * Patients with severe lactose intolerance. * Patients with more than 1 recurrence of CDAD during the 6 months prior to enrollment. * Patients unable to take oral medications. * Use within 1 week of enrollment of any drug or therapy with anti-C. difficile activity such as oral or intravenous metronidazole and oral vancomycin. \[Patients that have taken up to 3 doses of metronidazole or vancomycin can be included in the study\]. * Females of child bearing age who are either pregnant, breast-feeding or not using birth control and are sexually active. * Patients who are either clinically unstable (e.g., fulminant disease patients with signs of toxic megacolon, imminent perforation, colectomy or death) or unlikely to live throughout the 31-day duration of the study due to underlying illness. * History of hypersensitivity to nitazoxanide or vancomycin or any active ingredient in the formulations.